1. Field of The Invention
The present invention relates to graphite fittings for graphite tubing.
2. Description of The Related Art
Various materials and construction techniques have been combined to build tooling structures. Some structures use an aluminum honeycomb sandwiched between laminated board materials. This type of sandwich laminate board is utilized in an egg crating structure configuration to support a tooling/molding surface. Ventilation in this egg crating structure is a requirement for proper air circulation during the cure cycle heat up and cool-down. Ventilation in the egg crating structure occurs with holes through the sandwich laminate board. Tooling structures are also built of welded aluminum members, but the metal's response to temperature and pressure hinders accurate molding of products. A third tooling structure material is preimpregnated woven material formed into lengths of tubing. This tubing typically is square with two or four inch sides. These tubes are joined at various angles by fittings made of laminated board.
The above building materials for tooling structures have shortcomings. The aluminum honeycomb-laminated board combination is expensive, cumbersome, and labor intensive. Much effort goes into joining the honeycomb and the laminated board. Once joined, the tooling structure must be analyzed to determine where and how large ventilation holes will be cut in the structure.
The welded aluminum structure requires extensive skilled labor for welding the aluminum members to the designed shape. Once completed, the welded structure's large weight is a shortcoming.
The preimpregnated woven structural tubing overcomes many of the above shortcomings. The tubing is easily cut to required lengths, is light weight, and responds to temperature and pressure compatibly with parts molded on the graphite tooling structure. One drawback, however, to preimpregnated woven structural tubing has been the laminated board fittings used to join the graphite tubing in the designed tooling structure shape. These fittings responded to temperature and pressure differently than the tubing. Consequently, molded part production was unpredictable and uniformity in the parts impossible.
The present invention overcomes the problem arising from using a laminated board fitting with a graphite tubing tooling structure. The invention uses preimpregnated graphite woven material to preform standard fittings used in tooling structure construction. These fittings are rectangularly shaped but have only three sides. The fourth side is left open to speed tooling structure assembly and accommodate minor variations in tubing dimensions. Graphite tubing is inserted in the graphite fitting and held in place by drilling a hole through the fitting and graphite tubing and inserting a fastener, such as a nut and bolt combination or a blind fastener.
U.S. Pat. No. 3,392,947 and United Kingdom patent number GB 2 126 682 A disclose joining components for furniture. U.S. Pat. No. 3,392,947 describes rectangular structural members with tenons and mortises at joining points. GB 2 126 682 A describes furniture joints made of flat chip board panels. This furniture art is not particularly relevant to the graphite tooling structures built with the applicant s invention.
U.S. Pat. No. 4,379,798 discloses structural components formed of resin impregnated graphite webbing. The patent includes no suggestion for forming fittings of this resin impregnated fabric or for interconnecting structural components made of the resin impregnated fabric.
The present invention offers builders cf tooling structures lightweight, strong, versatile fittings which react compatibly with molded products under high temperatures and pressures.
Additional features, advantages and characteristics of the invention will become apparent from a reading of the following description or may be learned by practice of the invention.